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H5N1 avian influenza virus particles, coloured transmission electron micrograph (TEM). These particles were isolated from a human victim in Vietnam. The virus was first detected in birds in 2003 in South-East Asia and by early 2006 it had spread across much of Asia and Europe. It is carried by wild birds, which are generally not affected by it, but it is nearly always fatal to poultry and domestic birds. The virus is excreted in bird faeces, and humans inhaling faecal matter have contracted the disease, which had claimed around 100 lives by spring 2006. There are fears that it could mutate into a form capable of spreading directly from human to human, which could claim hundreds of thousands of lives. The name H5N1 relates to the subtypes of the viral surface proteins Haemagglutinin and Neuraminidase. Magnification: x130,000 when printed 10cm wide.